Contactless power transmission system for transmitting power from power transmitter apparatus to power receiver apparatus, and supplying load device with desired voltage

Abstract

A detection circuit detects at least one of a value of a current flowing through a power transmitting coil, and a value of a current or voltage generated by an auxiliary coil. A control circuit determines a transmitting frequency based on the value detected by the detection circuit, the transmitting frequency at least locally minimizing load dependence. The control circuit determines a voltage for the transmitting power at which an output voltage of a power receiver apparatus is equal to a predetermined target voltage when generating the transmitting power having the transmitting frequency determined, and controls the power supply circuit to generate the transmitting power having the transmitting frequency and voltage determined.

The invention claimed is: 
     
       1. A control apparatus for a power transmitter apparatus that transmits power to a power receiver apparatus comprising a power receiving coil, in a contactless manner,
 wherein the power transmitter apparatus comprises: a power transmitting coil, an auxiliary coil electromagnetically coupled to the power transmitting coil, and a power supply circuit that generates transmitting power having a variable voltage and a variable frequency and supplies the transmitting power to the power transmitting coil, 
 wherein the control apparatus comprises: 
 a detection circuit that detects at least one value of a value of a current flowing through the power transmitting coil, and a value of a current or voltage generated by the auxiliary coil; and 
 a control circuit that determines a transmitting frequency based on the at least one value detected by the detection circuit, the transmitting frequency at least locally minimizing dependence of an output voltage of the power receiver apparatus on a load value of the power receiver apparatus, determines a voltage for the transmitting power at which the output voltage of the power receiver apparatus is equal to a predetermined target voltage when generating the transmitting power having the determined transmitting frequency, and controls the power supply circuit to generate the transmitting power having the determined transmitting frequency and voltage. 
 
     
     
       2. The control apparatus for the power transmitter apparatus according to  claim 1 ,
 wherein the power receiver apparatus comprises a first load device having a variable load value, a second load device having a predetermined load value, and a switch circuit that selectively supplies the output voltage of the power receiver apparatus to one of the first load device and the second load device, 
 wherein the control apparatus further comprises a communication circuit communicatively connected to the power receiver apparatus, 
 wherein, when transmitting power in a normal manner, the control circuit transmits a signal to the power receiver apparatus using the communication circuit, the signal controlling the switch circuit to supply the output voltage of the power receiver apparatus to the first load device, and 
 wherein, when determining the transmitting frequency, the control circuit transmits a second signal to the power receiver apparatus using the communication circuit, the second signal controlling the switch circuit to supply the output voltage of the power receiver apparatus to the second load device, and determines the transmitting frequency based on the value detected by the detection circuit. 
 
     
     
       3. The control apparatus for the power transmitter apparatus according to  claim 1 , further comprising a coupling coefficient estimator that estimates a coupling coefficient between the power transmitting coil and the power receiving coil based on the at least one value detected by the detection circuit, and determines the transmitting frequency based on the coupling coefficient. 
     
     
       4. The control apparatus for the power transmitter apparatus according to  claim 3 ,
 wherein the detection circuit comprises a first detector that detects the value of the current or voltage generated by the auxiliary coil, and a second detector that detects the current flowing through the power transmitting coil, 
 wherein the coupling coefficient estimator estimates a first coupling coefficient between the power transmitting coil and the power receiving coil based on the value of the current or voltage generated by the auxiliary coil, and estimates a second coupling coefficient between the power transmitting coil and the power receiving coil based on the value of the current flowing through the power transmitting coil, and 
 wherein, when a difference between the first and second coupling coefficients is equal to or less than a predetermined threshold, the control circuit controls the power supply circuit to generate the transmitting power having the determined frequency and voltage. 
 
     
     
       5. The control apparatus for the power transmitter apparatus according to  claim 4 ,
 wherein, when the difference between the first and second coupling coefficients is greater than the predetermined threshold, the control circuit controls the power supply circuit to stop the power transmission to the power receiver apparatus. 
 
     
     
       6. A power transmitter apparatus comprising:
 a power transmitting coil; 
 an auxiliary coil electromagnetically coupled to the power transmitting coil; 
 a power supply circuit that generates transmitting power having a variable voltage and a variable frequency and supplies the transmitting power to the power transmitting coil; and 
 a control apparatus for the power transmitter apparatus, 
 wherein the power transmitter apparatus transmits power to a power receiver apparatus comprising a power receiving coil, in a contactless manner, 
 wherein the control apparatus comprises: 
 a detection circuit that detects at least one value of a value of a current flowing through the power transmitting coil, and a value of a current or voltage generated by the auxiliary coil; and 
 a control circuit that determines a transmitting frequency based on the at least one value detected by the detection circuit, the transmitting frequency at least locally minimizing dependence of an output voltage of the power receiver apparatus on a load value of the power receiver apparatus, determines a voltage for the transmitting power at which the output voltage of the power receiver apparatus is equal to a predetermined target voltage when generating the transmitting power having the determined transmitting frequency, and controls the power supply circuit to generate the transmitting power having the determined transmitting frequency and voltage. 
 
     
     
       7. The power transmitter apparatus according to  claim 6 , further comprising a capacitor connected to the power transmitting coil so as to form an LC resonant circuit. 
     
     
       8. The power transmitter apparatus according to  claim 6 , further comprising a magnetic core around which the power transmitting coil and the auxiliary coil are wound,
 wherein the auxiliary coil is disposed so as to surround the power transmitting coil. 
 
     
     
       9. A contactless power transmission system including:
 a power transmitter apparatus; and 
 a power receiver apparatus comprising a power receiving coil, 
 wherein the power transmitter apparatus comprises: 
 a power transmitting coil; 
 an auxiliary coil electromagnetically coupled to the power transmitting coil; 
 a power supply circuit that generates transmitting power having a variable voltage and a variable frequency and supplies the transmitting power to the power transmitting coil; and 
 a control apparatus for the power transmitter apparatus, 
 wherein the power transmitter apparatus transmits power to the power receiver apparatus in a contactless manner, 
 wherein the control apparatus comprises: 
 a detection circuit that detects at least one value of a value of a current flowing through the power transmitting coil, and a value of a current or voltage generated by the auxiliary coil; and 
 a control circuit that determines a transmitting frequency based on the at least one value detected by the detection circuit, the transmitting frequency at least locally minimizing dependence of an output voltage of the power receiver apparatus on a load value of the power receiver apparatus, determines a voltage for the transmitting power at which the output voltage of the power receiver apparatus is equal to a predetermined target voltage when generating the transmitting power having the determined transmitting frequency, and controls the power supply circuit to generate the transmitting power having the determined transmitting frequency and voltage.